1. Field of the Invention
The present invention generally relates to optical disks such as CD-Rs, DVD-Rs and DVD+Rs that use organic dye for a recording layer so that information can be written thereon. In such optical disks, the number of times of recording is once (Write Once) according to the characteristics of the organic dye used for the recording layer.
2. Description of the Related Art
It is possible to record/reproduce information to/from such optical disks by using an optical disk apparatus having a light emitting element emitting a laser beam and capable of properly varying the output power of the laser beam emitted from the light emitting element. For example, some conventional optical disk apparatuses perform real recording at optimum recording power by, before starting the real recording to an optical disk, test recording information to the optical disk, and obtaining the optimum recording power based on the characteristics of a reproduction signal obtained by reproducing a test recorded area. Hence, it is possible to achieve a good recording quality. Hereinafter, obtaining optimum recording power based on a reproduction signal from a test recorded area is referred to as OPC (Optimum Power Control). Also, the area on an optical disk that allows test recording in the OPC is referred to as a PCA (Power Calibration Area).
Recording sensitivity of an optical disk varies relatively drastically with respect to wavelength variation of the laser beam emitted from the light emitting element in recording. Thus, the optimum recording power varies in accordance with the wavelength variation of the laser beam emitted from the light emitting element. For this reason, recording quality for an optical disk also varies according to the wavelength variation of the laser beam.
By the way, the wavelength variation of the laser beam emitted from the light emitting element in recording is relatively drastic with respect to variation of environmental temperature. Consequently, when recording is performed at a different environmental temperature by using recording power that is optimum at a certain temperature, a case is conceived where the optimum recording power is not achieved even when the recording power with which the light emitting element performs emission is the same. Thus, there is concern that recording quality for an optical disk is degraded.
As for counter measures, conventionally, there is technology that maintains recording quality by setting again the recording power, pulse shape and the like (recording strategy), or performing test recording again when temperature in the vicinity of the optical disk apparatus having the light emitting element is measured, and the temperature in the vicinity of the optical disk apparatus changes to equal to or more than a predetermined temperature (refer to Japanese Laid-Open Patent Applications No. 2001-297437 and No. 2001-176141, for example).
In addition, there is conventional technology that detects the wavelength of the laser beam emitted from the light emitting element and drives the light emitting element according to the detected wavelength of the laser beam so as to correspond to the variation of the environmental temperature (refer to Japanese Laid-Open Patent Application No. 2001-297465, for example).
However, it is conceived that the relationship between the optimum recording power and the environmental temperature differs depending on variation of the optical disk apparatuses (especially, lasers), the kind of an optical disk, production lot, and the like. Accordingly, there is fear that the optimum recording power is not always obtained by obtaining a unique recording power from a temperature. As measures for this, it is preferable that the optimum recording power is obtained by performing the OPC every time real recording is performed.
On the other hand, it is highly possible that the PCA soon becomes full when the OPC is performed every time the environmental temperature varies, since the PCA is limited in an optical disk (Write Once medium) that includes the recording layer using organic dye and can be written to only once. When the PCA soon becomes full, test recording cannot be performed anymore. Accordingly, recording thereafter must be done without performing the OPC, though a normal real recording area still remains.